About 7 million couples in America have fertility problems, 40 to 50% of which are attributable to the male. Current methods of diagnosing male infertility by microscopic examination of the semen specimen are inadequate and more reliable tests need to be developed. The aim is to develop such a test by using a silica wool filtration technique. The method is based on the observation that the silica (glass) wool fibers filter out non-motile spermatozoa with chemically inactive or physically damaged membranes. Thus, with a simple one-step method, one can determine the number of viable spermatozoa in a semen sample without having to perform analyses for sperm motility, or the eosin Y stain, or the hypoosmotic swelling test. The number of viable spermatozoa in an ejaculate shoud be a good indication of the potential fertilizing capacity of the semen. Due to its simplicity, the filtration test can readily be used in private practice or under other conditions where trained technicians are not available. Phase I of the project is aimed at establishing the feasibility of the technique and evaluate whether it will yield consistent, reliable and reproducible results. Also, the correlation of this test with the zona-free hamster oocyte penetrating ability will be compared to that of the more standard parameters. Success with Phase I will indicate Phase II during which the in vivo (clinical) application and reliability of the test will be assessed as a predictor of infertility and fertility.